Method and system for improving wireless link efficiency

ABSTRACT

One embodiment of the present invention provides a system for improving transmission efficiency of a wireless link. During operation, the system receives a packet for transmission, where in the packet includes an original sequence number. The system then modifies the packet by including a virtual sequence number in a header of the packet and including the original sequence number in a payload of the modified packet. The system further aggregates a number of modified packets into an aggregate frame and transmits the aggregate frame to a destination device. The virtual sequence number facilitates stateless transmission of the encapsulated packets and allows the aggregate frame to have a maximum allowable number of packets while accommodating both re-transmitted packets and regular packets.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/830,385, Attorney Docket Number UBNT12-1012NP, entitled “METHOD ANDSYSTEM FOR IMPROVING WIRELESS LINK EFFICIENCY,” by inventors SriramDayanandan, Darius Ivanauskas, Mindaugas Kriauciunas, Antanas Gadeikis,and Kestutis Barkauskas, filed Mar. 14, 2013, which claims the benefitof U.S. Provisional Patent Application No. 61/729,219 (Attorney DocketNumber UBNT12-1012PSP), filed Nov. 21, 2012, entitled “METHOD AND SYSTEMFOR IMPROVING WIRELESS LINK EFFICIENCY.”

BACKGROUND

1. Field

This disclosure is generally related to wireless networks. Morespecifically, this disclosure is related to a method and system forimproving transmission efficiency in a wireless link.

2. Related Art

In recent years, the phenomenal growth of mobile devices, such as smartphones and tablet computers, has resulted in a huge demand in wirelessnetworks. Particularly, Wi-Fi networks, which are based on theIEEE-802.11 family of standards, are becoming increasingly ubiquitous.

In conventional wired layer-2 networks such as 10base-T, 100base-T, or1000base-T Ethernet, transmission of a packet is typically not followedby an acknowledgement from the receiver. Reliable data delivery dependson upper layer protocols, such as Transmission Control Protocol (TCP),to acknowledge the sender of received data packets, and to ensure thatthe sender retransmits a packet in the event of a failed transmission.

Wireless networks such as IEEE 802.11a/b/g/n/ac networks, however,require explicit acknowledgement from the receiver for every packet dueto the unreliable nature of the communication medium. In addition, IEEE802.11a/b/g/n/ac networks use carrier sense multiple access withcollision avoidance (CSMA/CA) before beginning any transmission in orderto avoid collision with other transmitters. These requirements oftenlead to low transmission efficiency in IEEE 802.11 wireless links.

SUMMARY

One embodiment of the present invention provides a system for improvingtransmission efficiency of a wireless link. During operation, the systemreceives a packet for transmission, where in the packet includes anoriginal sequence number. The system then modifies the packet byincluding a virtual sequence number in a header of the packet andincluding the original sequence number in a payload of the modifiedpacket. The system further aggregates a number of modified packets intoan aggregate frame and transmits the aggregate frame to a destinationdevice. The virtual sequence number facilitates stateless transmissionof the encapsulated packets and allows the aggregate frame to have amaximum allowable number of packets while accommodating bothre-transmitted packets and regular packets.

In a variation on this embodiment, the aggregate frame includes packetsassociated with different original traffic categories.

In a variation on this embodiment, the packet includes an originaltraffic category indicator. In addition, modifying the packet furtherinvolves including a virtual traffic category indicator in the header ofthe packet and including the original traffic category indicator in thepayload of the modified packet.

In a further variation, all the modified packets in the aggregate framehave the same virtual traffic category indicator.

In a variation on this embodiment, the system monitors an error rate fora respective original traffic category.

In a further variation, the system duplicates, in the aggregate frame, anumber of modified packets associated with the original traffic categoryfor which the error rate is monitored, in response to the error ratesurpassing a predetermined threshold.

In a variation on this embodiment, the wireless link is an IEEE 802.11wireless link.

One embodiment of the present invention provides a system for improvingtransmission efficiency of a wireless link. During operation, the systemreceives an aggregate frame which comprises a number of modifiedpackets. Each modified packet includes a virtual sequence number and avirtual traffic category identifier in the packet's header, and anoriginal sequence number and an original traffic category identifier inthe modified packet's payload. The system then de-aggregates themodified packets from the aggregate frame. Next, the system decapsulatesall the modified packets and orders the decapsulated packets based ontheir original sequence number and original traffic category indicator.

In a variation on this embodiment, the original sequence numbers of thepackets in the aggregate frame are non-continuous.

In a variation on this embodiment, the packets in the aggregate frameare associated with different original traffic categories.

In a variation on this embodiment, the virtual sequence numbers of thepackets in the aggregate frame are continuous.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A illustrates an example of transmitting three packets in an IEEE802.11a/b/g network.

FIG. 1B illustrates an example of transmitting three aggregate frames inan IEEE 802.11n network.

FIG. 2A illustrates a retransmission process in a conventional wirelessnetwork where the first four packets in an aggregate frame, whichincludes 64 packets, are not received successfully.

FIG. 2B illustrates a retransmission process in a conventional wirelessnetwork where four packets in the middle of an aggregate frame, whichincludes 64 packets, are not received successfully.

FIG. 2C illustrates a retransmission process in a conventional wirelessnetwork where four packets in the tail of an aggregate frame, whichincludes 64 packets, are not received successfully.

FIG. 3A presents a block diagram illustrating the operation ofaggregating multiple packets and transmitting the aggregate frame over awireless link to a receiver.

FIG. 3B illustrates a conventional IEEE 802.11n packet header format.

FIG. 4A presents a block diagram illustrating the operation ofaggregating multiple packets with virtual sequence headers andtransmitting the aggregate frame over a wireless link to a receiver, inaccordance with one embodiment of the present invention.

FIG. 4B presents a modified IEEE 802.11n header that facilitates virtualsequence number and virtual traffic ID (TID), in accordance with oneembodiment of the present invention.

FIG. 5 presents a flowchart illustrating the process of reserving packetslots in an aggregate frame based on detected packet error rateassociated with a traffic category, in accordance with one embodiment ofthe present invention.

FIG. 6 illustrates an exemplary transceiver system that facilitatesvirtual sequence number for wireless transmission in an IEEE 802.11wireless link, in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled inthe art to make and use the embodiments, and is provided in the contextof a particular application and its requirements. Various modificationsto the disclosed embodiments will be readily apparent to those skilledin the art, and the general principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the present disclosure. Thus, the present invention is notlimited to the embodiments shown, but is to be accorded the widest scopeconsistent with the principles and features disclosed herein.

Some embodiments of the present invention enhance the transmissionefficiency in IEEE 802.11 wireless links by using virtual sequencenumbers for packets transmitted in an aggregate frame, which allowspackets to be retransmitted with other regular packets in an aggregateframe that can accommodate the maximum number of packets. In particular,the virtual sequence number can be arbitrary, and be selected in such away that allows any number of packets to be retransmitted with otherregular packets in the same aggregate frame which is not limited by theacknowledgement window and can be filled up to the maximum allowablenumber of packets.

As mentioned earlier, the fact that IEEE 802.11 networking standardsrequire per-packet acknowledgement, and that the transmission is basedon CSMA/CA, results in fairly inefficient utilization of the wirelessbandwidth, regardless of how high the transmission data rate is. Suchinefficiencies are illustrated in the examples presented in FIGS. 1A and1B.

FIG. 1A illustrates an example of transmitting three packets in an IEEE802.11 a/b/g network, which does not provide aggregated packettransmission. In this example, when a transmitter has packets totransmit, it first waits for a fixed amount of delay (denoted asarbitration inter-frame spacing, AIFS). The AIFS duration may vary basedon traffic category. After AIFS, the transmitter further waits for arandom period of time, denoted as random backoff 101. During randombackoff 101, if the transmitter detects another transmission via thesame communication medium, the transmitter will wait until the detectedtransmission is finished, and then continues the random backoff 101countdown.

After random backoff 101, the transmitter can transmit a packet 102.After receiving packet 102, the receiver waits for a small time interval(denoted as short interframe space, SIFS), before sending anacknowledgement 104. Subsequently, the transmitter waits for anotherAIFS and random backoff before transmitting a packet 106.

Correspondingly, the receiver waits for an SIFS before sending ACK 108.In the same manner, the transmitter can transmit the next packet 110,and receives a corresponding acknowledgement 112.

As can be seen in the example in FIG. 1A, the transmission of a singlepacket requires a significant amount of idle waiting (AIFS, randombackoff, and SIFS). Furthermore, each packet requires a separate ACK.These requirements incur a significant overhead for transmission.

To mitigate such inefficiency, the IEEE 802.11n standard introducedpacket aggregation and block acknowledgement mechanism. With packetaggregation, an aggregate frame includes multiple packets to the samedestination , which are combined into a single transmission unit.Typically, an aggregate frame can include up to 64 packets. After thetransmission, the receiver waits for a fixed amount of delay (SIFS)before sending a block acknowledgement (BLOCK ACK). A BLOCK ACK containsa beginning sequence number, which corresponds to the sequence number ofthe earliest packet in the aggregate frame, and a bitmap corresponds toall the packets encapsulated in the aggregate frame. Note that a BLOCKACK can only acknowledge a continuous number of packets, due to thesequential nature of the bitmap.

FIG. 1B illustrates an example of transmitting three aggregate frames inan IEEE 802.11n network. In this example, after waiting for AIFS and arandom backoff period, the transmitter transmits aggregate frame 122.Subsequently, the receiver waits for SIFS and sends back a BLOCK ACK124. A similar process take place when the transmitter transmitsaggregate frame 126 and aggregate frame 130. The receiver sends backcorresponding BLOCK ACKS 128 and 132.

Ideally, the packet aggregation mechanism in IEEE 802.11n is expected toimprove the transmission efficiency of the wireless link to about 65%,compared with 40% in IEEE 802.11a/b/g. This improvement is mainly due tothe amortization of the various overhead over a group of packets in802.11n, as opposed to a single packet in 802.11a/b/g.

However, the aggregation and block acknowledgement mechanism in 802.11nstill have some drawbacks. The transmitter and receiver typicallynegotiate the BLOCK ACK window (BAW), which is the maximum length of thetransmission history for retransmissions. This window imposes a limit onthe end throughput. Furthermore, the packet aggregation is on aper-traffic category (or traffic category) basis (in 802.11nterminology, on a per traffic identifier, or TID, basis,). Hence, whenthe transmitter has two traffic from two or more different categories(e.g., voice and data), the transmission efficiency is further reduced.

FIGS. 2A, 2B, and 2C illustrate how the BAW can restrict the endthroughput. FIG. 2A illustrates a retransmission process in aconventional wireless network where the first four packets in anaggregate, which includes 64 packets, are not received successfully. Inthis example, the sender transmits an aggregate frame containing 64packets with the same TID, with sequence numbers 1 to 64. Packets withsequence numbers 65 and up are stored in a queue, assuming that the BAWis 64. Assume that the receiver receives the aggregate frame. However,packets 1 to 4 are received with an error (as indicated by a shadedpattern in FIG. 2A). The receiver then sends the BLOCK ACK to thesender. In response, the sender retransmits packets 1 to 4 in the nextaggregate frame. However, since the BAW is 64, and since the BLOCK ACKcan only acknowledge a group of continuous 64 packets, the retransmittedaggregate frame cannot accommodate any packet with sequence numberhigher than 64. Hence, the total number packets in the retransmittedaggregate frame is 4, and the aggregate frame cannot carry any newpacket. This error scenario can reduce the link efficiency by 50%.

FIG. 2B illustrates a retransmission process in a conventional wirelessnetwork where four packets in the middle of an aggregate frame, whichincludes 64 packets, are not received successfully. In this example, thesender transmits an aggregate frame with packets of sequence numbers 1to 64. After the receiver receives the aggregate frame, assume thatpackets 15 to 18 are in error. The receiver then sends a BLOCK ACK tothe sender indicating that these four packets need to be retransmitted.In response, the sender assembles a retransmission aggregate frame,starting with packets 15 to 18. In addition, the sender can also includepackets 65 to 78 in the same aggregate frame, as allowed by the BAW(that is, the receiver can subsequently acknowledge packets 15 to 78).In this scenario, the total number of packets in the retransmissionframe is 18, 14 of which are new packets. The link efficiency is reducedby 40% due to the above error scenario.

FIG. 2C illustrates a retransmission process in a conventional wirelessnetwork where four packets in the tail of an aggregate frame, whichincludes 64 packets, are not received successfully. In this example, thesender initially sends packets 1 to 64. Assume that packets 61 to 64 arereceived in error. The receiver then sends back a BLOCK ACK indicatingthat packets 61 to 64 need to be retransmitted. In response, the senderassembles a retransmission aggregate frame, which contains packets 61 to64. In addition, the sender can also include frames 65 to 124 in thesame aggregate frame, since the BAW allows 64 continuous packets. Hence,in this scenario, the retransmission frames includes a total number of64 packets, 60 of which are new packets. The link efficiency is reducedby only 4% due to the above error scenario.

As illustrated in the examples above, the wireless link's transmissionefficiency can vary from 50% to 96% of its designed value, even with apacket error rate as low as 6.25% (4 error packets out of 64). This isbecause the BLOCK ACK can only acknowledge a group of continuouspackets, which prevents the retransmission aggregate frame from fullyutilizing the maximum slots allowed by the BAW. Real-world wirelesslinks, especially outdoor ones, can exhibit far higher packet errorrates, resulting in further degraded link efficiency.

A further limitation of the 802.11n aggregation mechanism is that itonly allows an aggregate frame to carry packet from the same trafficcategory (i.e., with the same TID). For example, if the sender needs totransmit 64 packets in TID 0 and 2 packets in TID 1. Assuming TID 1 isassociated with a higher priority than TID 0, the sender will assemble afirst aggregate frame with only 2 packets from TID 1, despite the factthat it has 64 packets in TID 0 waiting to be transmitted. Theseaggregate frames still need to go through the standard fixed/randomdelays and BLOCK ACK mechanisms separately. Hence, even under excellenttransmission conditions the link usage efficiency is reduced.

Embodiments of the present invention solve the aforementioned problemsby using virtual sequence numbers and virtual TIDs in the aggregateframe, which allows the sender to fully utilize the maximum number ofpacket slots in an aggregate frame allowed by the BAW, even whenretransmitting packets. The original sequence number and TID are movedto the payload portion of each 801.11n packet. The sequence number andTID fields in each packet's 802.11n header are updated with the virtualsequence number and TID values. FIG. 3A and its correspondingdescription below explain the operation of transmitter and receiver inaccordance with the existing 802.11n standard. FIG. 4 and itscorresponding description explain the operation of the transmitter andreceiver using the virtual sequence numbers and TIDs, in accordance withembodiments of the present invention.

In the example illustrated in FIG. 3A, a transmitting station 301includes a network protocol stack 302, and 802.11 encapsulation module304, a set of per TID queues 306, a per TID aggregation release module308, and a transmitter 310. A receiving station 321 includes a receiver312, a set of per-TID de-aggregation reorder buffers 314, a per TIDde-aggregation release module 316, a 802.11 decapsulation module 318,and a network protocol stack 320.

During operation, network protocol stack 302 assembles traffic fromupper layers (such as TCP/IP) into layer-2 packets. 802.11 encapsulationmodule 304 encapsulates the packets with 802.11 headers (which aredescribed in more detail in conjunction with FIG. 3B). Per TIDaggregation queues 306 temporarily store the packets, based on theirrespective TIDs, in separate queues while waiting for the transmissionmedium to be available for transmission (e.g., when the system waits forAIFS and random backoff). When the transmission medium becomes availablefor transmission, per TID aggregation release module 308 selects aTID-specific queue (which can be based on a traffic prioritizationpolicy) and releases an aggregate frame which contains packets from theselected queue. Transmitter 310 then transmits the aggregate frame via awireless link to receiver 312.

After receiver 312 receives the aggregate frame, the packets in theaggregate frame are de-aggregated, reordered, and stored in one of theper TID buffers 314. The packets are temporarily stored in per TIDbuffers 314 while waiting for the upper-layer modules are ready toretrieve the packets. Subsequently, per TID de-aggregation releasemodule 316 releases the packets in a particular per TID buffer, uponwhich 802.11 decapsulation module 318 removes the 802.11 headers fromthe packets. Subsequently, the decapsulated packets are forwarded tonetwork protocol stack 320.

FIG. 3B illustrates a conventional IEEE 802.11n packet header format. Asmentioned above, each packet is encapsulated with an IEEE 802.11n headerbefore it is aggregated into an aggregate frame. As illustrated in FIG.3B, an IEEE 802.11n header includes a frame control (FC) field, aduration/ID (DUR-ID) field, four address fields (ADDR1, ADDR2, ADDR3,and ADDR4), a sequence control field (SEQ-CTRL), a QoS control field(QOS-CTRL), and a SubNetwork Access Protocol header (SNAP-HDR).

The FC field contains control information used for defining the type of802.11 MAC frame and providing information necessary for the followingfields to understand how to process the MAC frame.

The DUR-ID field is used for all control type frames, except with thesubtype of Power Save (PS) Poll, to indicate the remaining durationneeded to receive the next frame transmission. When the sub-type is PSPoll, the field contains the association identity (AID) of thetransmitting station.

Depending on the frame type, the four address fields can contain acombination of the following address types: base service setidentification (BSSID), destination address (DA), source address (SA),receiver address (RA), and transmitter address (TA).

The SEQ-CTRL field includes a sequence number and a fragment number. Thesequence number indicates the sequence number of each packet. Thesequence number is the same for each packet sent from a fragmentedpacket. Otherwise, the sequence number is incremented by one until itreaches 4095, when it begins at zero again. The fragment numberindicates the number of each frame sent that belongs to a fragmentedframe.

The QOS-CTRL field indicates the QoS parameters of the packet. Inparticular, the QOS-CTRL field includes a TID subfield, which indicatesthe traffic category.

In embodiments of the present invention, on the transmission side, theprocess of per TID aggregation release is now replaced by a multi-TIDaggregation release process. Furthermore, a packet's sequence number inthe 802.11n header is now replaced with a virtual sequence number, andthe packet's original sequence number is moved inside the payload of theencapsulated 802.11n packet.

FIG. 4A presents a block diagram illustrating the operation ofaggregating multiple packets with virtual sequence headers andtransmitting the aggregate frame over a wireless link to a receiver, inaccordance with one embodiment of the present invention. In thisexample, a transmitting station 401 includes a network protocol stack402, which provides the packets to be encapsulated in 802.11n headers byan IEEE 802.11 encapsulation module 404. Note that at this stage, thepackets still retain their original sequence numbers and TIDs.Subsequently, the 802.11n encapsulated packets are buffered in a set ofper TID aggregation queues 406 while transmitting station 401 waits forthe transmission medium to become available. When the medium becomesavailable, a multi-TID aggregation release module retrieves a number ofpackets from per TID queues 406. Note that the aggregate frame maycontain packets associated with different TIDs, and these packets'sequence numbers can be non-continuous within each TID. As long as thereare a sufficient number of packets buffered in aggregation queues 406,multi-TID aggregation release module 408 can always release the maximumnumber of packets allowed by the BAW. Note that in some embodimentspackets belonging to higher-priority TIDs are released for assemblybefore those of lower-priority TIDs. Furthermore, both retransmittedpackets and new packets can be released, without the constraint ofhaving all the packets in the aggregate frame being continuous and fromthe same TID.

Next, a virtual sequence header encapsulation module 409 updates thesequence number field and TID field in each packet's 802.11n header witha virtual sequence number and a virtual TID number, respectively. Forall the packets in a given aggregate frame, their virtual sequencenumbers are continuous (for example, from 1 to 64). All the packets inthe aggregate frame also have the same virtual TID value. In addition,while updating the sequence number and TID field for each packet,virtual sequence header encapsulation module 409 also moves the packet'soriginal sequence number and TID into the payload portion of the 802.11necapsulated packet. More details on the modified 802.11n header formatare provided below in conjunction with FIG. 4B.

The aggregate frame, which contains all the released and modifiedpacket, is then provided to a transmitter 410, which transmits theaggregate frame over a wireless link to a receiving station 421. After areceiver 412 receives the aggregate frame, a virtual sequence headerdecapsulation module 413 decapsulates the aggregate frame and restoresthe original sequence number and TID in the 802.11n header for eachpacket. Subsequently, the packets are reordered and buffered in a set ofper TID de-aggregation reorder buffers 414. A per TID de-aggregationrelease module 416 then releases the packets from buffers 414 to a802.11 decapsulation 418, which removes a packet's 802.11n header andforwards the packet to a network protocol stack 420. Note that receivingstation 421 responds back to transmitting station 421 with a blockacknowledgement containing a bitmap corresponding to the virtualsequence numbers.

FIG. 4B presents a modified IEEE 802.11n header that facilitates virtualsequence number and virtual traffic ID (TID), in accordance with oneembodiment of the present invention. In this example, an 802.11n header504's SEQ-CTRL field contains the virtual sequence number. In addition,header 504's QOS-CTRL field contains the virtual TID. An additionalvirtual sequence control field 506 (VSEQ-CTRL), which in one embodimentcan be four bytes long, is inserted after the QOS-CTRL field (theposition where conventional packet payload begins). VSEQ-CTRL field 506contains the packet's original sequence number and TID.

Because the virtual sequence numbers do not have actual meanings and areonly used to allow the receiving station to send a BLOCK ACK thatacknowledges all the packets in the aggregate frame, the virtualsequence numbers can be restarted for every transmission. In otherwords, the transmission can be stateless. Note that the transmittingstation might need to retain the virtual-to-original sequence number andTID mapping until the BLOCK ACK is received, so that in case oftransmission error the transmitting station can identify the correctpackets to retransmit.

Because of the flexibility afforded by the virtual sequence number andTID, the transmitting station can reserve packet slots in the aggregateframe for redundancy purposes, in order to mitigate non-idealtransmission conditions. For example, the transmitting station mayrandomly select 20% of the highest-priority packets and duplicate themin each aggregate frame to reduce the total packet error rate, if thepacket error rate surpasses a predetermined threshold. Furthermore, thetransmitting station can monitor the packet error rate for each TID, anddynamically replicate packets for each TID based on a predetermined QoSpolicy. When allocating reserved packet slots for duplicate packets, thetransmitting station can use various methods (such as strict prioritybased or round robin) to ensure the desired QoS parameters are met.

FIG. 5 presents a flowchart illustrating the process of reserving packetslots in an aggregate frame based on detected packet error rateassociated with a traffic category, in accordance with one embodiment ofthe present invention. During operation, a transmitting station firstassembles and transmits a multi-TID aggregate frame (operation 502). Thetransmitting station then receives a BLOCK ACK from the receivingstation (operation 504). Based on the received BLOCK ACK, thetransmitting station updates its record of per-TID packet error rate(operation 506). The transmitting station then determines, for each TID,whether the packet error rate is greater than a threshold for that TID(operation 508). If so, the transmitting station reserves a number ofpacket slots in the aggregate frame for duplicate packets of that TID(operation 510) prior to resuming transmission (operation 512). If theper-TID packet error rate is below the threshold, the transmittingstation resumes transmission (operation 512). The process repeats itselfby looping back to operation 502.

FIG. 6 illustrates an exemplary transceiver system that facilitatesvirtual sequence number for wireless transmission in an IEEE 802.11wireless link, in accordance with one embodiment of the presentinvention. In this example, a wireless transceiver system 600 includes aprocessor 602, a memory 604, and a communication module 606. Alsoincluded in transceiver system 600 are a virtual sequence number and TIDencapsulation/decapsulation module 608, a QoS management module 610, andan aggregation management module 612.

Communication module 606 may include a wireless radio that isresponsible for transmitting and receiving physical signals. Virtualsequence number and TID encapsulation/decapsulation module 608 isresponsible for modifying the 802.11n headers to include virtualsequence numbers and virtual TIDs, and for restoring a packet's originalsequence number and TID on the receiving side. QoS management module 610is responsible for enforcing any QoS policy. Aggregation managementmodule 612 is responsible for assembling aggregate frames and handlingretransmission in case of packet error.

Note that virtual sequence number and TID encapsulation/decapsulationmodule 608, QoS management module 610, and aggregation management module612 may be implemented in software, which means they can be based oninstructions stored in a storage device, loaded into memory 604, and,when executed by processor 602, perform the functions described above.These modules can also be implemented partly or entirely in hardware,using application specific integrated circuits (ASICs) or fieldprogrammable logic arrays (FPGAs).

The methods and processes described in the detailed description sectioncan be embodied as code and/or data, which can be stored in acomputer-readable storage device as described above. When a computersystem reads and executes the code and/or data stored on thecomputer-readable storage device, the computer system performs themethods and processes embodied as data structures and code and storedwithin the computer-readable storage medium.

Furthermore, methods and processes described herein can be included inhardware modules or apparatus. These modules or apparatus may include,but are not limited to, an ASIC chip, an FPGA, a dedicated or sharedprocessor that executes a particular software module or a piece of codeat a particular time, and/or other programmable-logic devices now knownor later developed. When the hardware modules or apparatus areactivated, they perform the methods and processes included within them.

Although the examples presented herein are based on IEEE 802.11nwireless links, embodiments of the present invention are not limitedonly to such links. Other types of wireless links based on existing orfuture standards (including IEEE 802.11 family and other protocols) canalso use various embodiments of the present invention. The claims hereinshould be not be interpreted as being limited only to IEEE 802.11nwireless links.

The foregoing descriptions of various embodiments have been presentedonly for purposes of illustration and description. They are not intendedto be exhaustive or to limit the present invention to the formsdisclosed. Accordingly, many modifications and variations will beapparent to practitioners skilled in the art. Additionally, the abovedisclosure is not intended to limit the present invention.

What is claimed is:
 1. A method of wireless link transmission,comprising: receiving a number of packets for transmission, wherein eachof the packets includes an original sequence number and an originaltraffic category indicator, and wherein the packets can havenon-continuous original sequence numbers and different original trafficcategory indicators; aggregating the packets into an aggregate frame;for each of the packets in the aggregate frame, modifying the packet byincluding a virtual sequence number and a virtual traffic categoryindicator in a header of the packet, and including the original sequencenumber and the original traffic category indicator in a payload of themodified packet; and transmitting the aggregate frame with modifiedpackets to a destination device through a wireless link.
 2. The methodof claim 1, wherein all the modified packets in the aggregate frame havethe same virtual traffic category indicator and continuous virtualsequence numbers.
 3. The method of claim 1, wherein the wireless link isan IEEE 802.11 wireless link.
 4. The method of claim 1, furthercomprising monitoring a packet error rate for a respective originaltraffic category.
 5. The method of claim 4, further comprisingduplicating, in the aggregate frame, a number of packets associated withthe original traffic category for which the error rate is monitored, inresponse to the error rate surpassing a predetermined threshold.
 6. Amethod of wireless link transmission, comprising: receiving an aggregateframe which comprises a number of modified packets, wherein eachmodified packet includes a virtual sequence number and a virtual trafficcategory identifier [It may be better to change “identifier” to“indicator” for consistency throughout the claims.] in the packet'sheader, and an original sequence number and an original traffic categoryidentifier in the modified packet's payload; de-aggregating the modifiedpackets from the aggregate frame; decapsulating all the modifiedpackets; and ordering the decapsulated packets based on their originalsequence number and original traffic category indicator.
 7. The methodof claim 6, wherein the wireless link is an IEEE 802.11 wireless link.8. A system of wireless link transmission, comprising: a networkprotocol stack operable to receive a number of packets for transmission,wherein each of the packets includes an original sequence number and anoriginal traffic category indicator, and wherein the packets can havenon-continuous original sequence numbers and different original trafficcategory indicators; an aggregation release module operable to aggregatethe received packets into an aggregate frame; and a virtual sequenceheader encapsulation module operable to modify each of the packets byincluding a virtual sequence number and a virtual traffic categoryindicator in a header of the packet, and including the original sequencenumber and the original traffic category indicator in a payload of themodified packet; and a transmitter operable to transmit the modifiedaggregate frame to a destination device.
 9. The system of claim 8,wherein all the modified packets in the aggregate frame have the samevirtual traffic category indicator and continuous virtual sequencenumbers.
 10. The system of claim 8, wherein the wireless link is an IEEE802.11 wireless link.
 11. The system of claim 8, further comprising amonitoring module operable to monitor an error rate for a respectiveoriginal traffic category.
 12. The system of claim 10, wherein theaggregation release module is further operable to duplicate, in theaggregate frame, a number of packets associated with the originaltraffic category for which the error rate is monitored, in response tothe error rate surpassing a predetermined threshold.
 13. A system ofwireless link transmission, comprising: a receiver operable to receivean aggregate frame which comprises a number of packets, wherein eachpacket includes a virtual sequence number and a virtual traffic categoryindicator in the packet's header, and an original sequence number and anoriginal traffic category indicator in the packet's payload, and whereinthe packets in the aggregate frame can have non-continuous originalsequence numbers and different original traffic category indicators; adecapsulation module operable to restore the original sequence numberand the original traffic category indicator in the header of each of thepackets; and a de-aggregation release module operable to de-aggregatethe packets from the aggregate frame and reorder the restored packetsbased on their original sequence number and original traffic categoryindicator.
 14. The system of claim 13, wherein the wireless link is anIEEE 802.11 wireless link.